Zero-Profile Interbody Spacer and Coupled Plate Assembly

ABSTRACT

An implant for insertion into a disc space between vertebrae, wherein the implant includes a spacer portion, a plate portion coupled to the spacer portion, two bone fixation elements for engaging the vertebrae and a retention mechanism for preventing the bone fixation elements from postoperatively backing-out of the plate portion. The retention mechanism may be in the form of a spring biased snapper element that is biased into communication with the bone fixation elements so that once the bone fixation element advances past the snapper element, the snapper element is biased back to its initial position in which the snapper element interfaces with the bone fixation elements. Alternatively, the retention mechanism may be in the form of a propeller rotatable between a first position in which the bone fixation elements are insertable to a second position where the bone fixation elements are prevented from backing-out.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/613,866, filed Nov. 6, 2009, entitled “Zero-Profile Interbody Spacerand Coupled Plate Assembly”, which claims priority to U.S. ProvisionalPatent Application No. 61/112,441, filed Nov. 7, 2008, entitled“Zero-Profile Interbody Spacer and Coupled Plate Assembly” and U.S.Provisional Patent Application No. 61/139,920, filed Dec. 22, 2008,entitled “Screw and Plate Locking Mechanisms for Smaller Bone Plates”,the contents of which are hereby incorporated by reference in theirentireties.

BACKGROUND OF THE INVENTION

Intervertebral implants including interbody spacer portions andmechanically coupled plate portions are known in the art for restoringdisc height, allowing fusion to occur between the adjacent vertebralbodies, and for providing stable fixation during healing.

It is desirable to construct a zero-profile implant wherein bonefixation elements that secure the implant to the vertebral bodies areblocked from backing-out of the bone and/or plate.

Additionally, it is desirable to construct a zero-profile implant thatincludes polyaxial bone fixation element couplings and features thatprevent the implant from being implanted too deeply into a prepared discspace. Both screw back-out and over-insertion of the implant into aprepared disc space can have an adverse impact on the performance of theimplant.

BRIEF SUMMARY OF THE INVENTION

The present invention relates generally to a spinal implant. Morespecifically, the present invention relates to a zero profile interbodyspacer and coupled plate assembly for insertion into a disc spacebetween adjacent superior and inferior vertebral bodies. The implantpreferably includes a spacer portion, a plate portion coupled to thespacer portion, a plurality of bone fixation elements for engaging thevertebral bodies and a retention mechanism for preventing the bonefixation elements from postoperatively uncoupling from the implant.

In one exemplary embodiment, the implant includes first and second bonefixation elements, a spacer portion, a plate portion coupled to thespacer portion, and first and second spring-biased snapper elements forpreventing the first and second bone fixation elements from backing-outof bone fixation holes formed in the plate portion (e.g., frompostoperatively uncoupling from the implant). The spacer portionpreferably includes a top surface for contacting the superior vertebralbody, a bottom surface for contacting the inferior vertebral body, afirst side surface, a second side surface, a leading surface and atrailing surface.

The plate portion includes a top surface, a bottom surface, a first sidesurface, a second side surface, a leading surface, a trailing surface,first and second bone fixation holes and first and second boreholes. Thefirst and second bone fixation holes are sized and adapted for receivingthe first and second bone fixation elements, respectively. The firstbone fixation hole is angled so that the first bone fixation elementengages the superior vertebral body while the second bone fixation holeis angled so that the second bone fixation element engages the inferiorvertebral body. The first borehole is in communication with the firstbone fixation hole and the second borehole is in communication with thesecond bone fixation hole.

The first and second spring-biased snapper elements are located in thefirst and second boreholes, respectively. The first and second springbiased snapper elements are moveable from a first position to a secondposition. In the first position, at least a portion of the first andsecond snapper elements protrude into the first and second bone fixationholes, respectively, so that once the first and second bone fixationelements have been inserted into the first and second bone fixationholes, respectively, the first and second snapper elements at leastpartially cover the first and second bone fixation elements,respectively, to prevent backing-out. The first and second spring biasedsnapper elements are preferably biased to the first position.

Preferably, insertion of the first and second bone fixation elementscauses a head portion of the first and second bone fixation elements tocontact the first and second spring biased snapper elements,respectively, to cause the first and second spring biased snapperelements to recoil from their first positions to the their secondpositions. Thereafter, further insertion of the first and second bonefixation elements causes the head portions of the first and second bonefixation elements to move distally of the first and second spring biasedsnapper elements resulting in the first and second snapper elementsautomatically moving from their second position to their first position.

The implant preferably further includes first and second stops toprevent over-insertion of the implant during implantation and to assistin securing a position of the implant during insertion of the first andsecond bone fixation elements. The first stop preferably extendssuperiorly of the top surface of the plate portion for contacting thesuperior vertebral body while the second stop extends inferiorly of thebottom surface of the plate portion for contacting the inferiorvertebral body. The first and second stops are preferably integrallyformed with the plate portion.

In another exemplary embodiment, the implant preferably includes firstand second bone fixation elements, a spacer portion, a plate portioncoupled to the spacer portion and a propeller element for preventing thefirst and second bone fixation elements from backing-out andover-insertion of the plate portion. The spacer portion includes a topsurface for contacting the superior vertebral body, a bottom surface forcontacting the inferior vertebral body, a first side surface, a secondside surface, a leading surface and a trailing surface.

The plate portion includes a top surface, a bottom surface, a first sidesurface, a second side surface, a leading surface, a trailing surface,and first and second bone fixation holes. The first and second bonefixation holes are sized and adapted for receiving the first and secondbone fixation elements, respectively. The first bone fixation hole isangled so that the first bone fixation element engages the superiorvertebral body while the second bone fixation hole is angled so that thesecond bone fixation element engages the inferior vertebral body.

The propeller preferably includes a longitudinal axis extending betweena first end and a second end. The propeller is coupled to the plateportion in-between the first and second bone fixation holes. In use, thepropeller is rotatable between a first position wherein the propellerdoes not interfere with first and second bone fixation holes so that thefirst and second bone fixation elements can be inserted into the firstand second bone fixation holes, respectively, to a second positionwherein the first end of the propeller at least partially covers atleast a portion of the first bone fixation hole and the second end ofthe propeller at least partially covers at least a portion of the secondbone fixation hole to prevent backing-out of the first and second bonefixation elements once implanted. The propeller is preferably rotatedthrough a range of about ninety degrees (90°) from the first position tothe second position. The propeller preferably includes a threaded screwfor engaging a threaded borehole formed in the plate portion. In use, inthe first position, the longitudinal axis of the propeller is preferablyoriented generally parallel to an axis of the implant and parallel to acranial-caudal axis of the vertebral bodies so that the first end of thepropeller extends superiorly of the top surface of the plate portion andthe second end of the propeller extends inferiorly of the bottom surfaceof the plate portion so that the propeller acts as a stop duringimplantation of the implant to prevent over-insertion and to assist insecuring a position of the implant during insertion of the first andsecond bone fixation elements.

In another exemplary embodiment, the implant sized and adapted forinsertion into an intervertebral disc space between superior andinferior vertebral bodies includes: (a) first and second bone fixationelements; (b) a spacer portion including a top surface for contactingthe superior vertebral body, a bottom surface for contacting theinferior vertebral body, a first side surface, a second side surface, aleading surface and a trailing surface; and (c) a plate portion coupledto the spacer portion. The plate portion including a top surface, abottom surface, a first side surface, a second side surface, a leadingsurface and a trailing surface. The plate portion further includingfirst and second bone fixation holes and first and second boreholes, thefirst and second bone fixation holes sized and adapted for receiving thefirst and second bone fixation elements, respectively. The first bonefixation hole is angled so that the first bone fixation element engagesthe superior vertebral body while the second bone fixation hole isangled so that the second bone fixation element engages the inferiorvertebral body. The first borehole is in communication with the firstbone fixation hole and the second borehole is in communication with thesecond bone fixation hole. The implant further including first andsecond spring-biased snapper elements for preventing the first andsecond bone fixation elements, respectively, from backing out. The firstspring biased snapper element is located in the first borehole and thesecond spring biased snapper element is located in the second borehole.The first and second spring biased snapper elements are moveable from afirst position to a second position, in the first position, at least aportion of the first and second snapper elements protrude into the firstand second bone fixation holes, respectively, so that once the first andsecond bone fixation elements have been inserted into the first andsecond bone fixation holes, respectively, the first and second snapperelements at least partially cover the first and second bone fixationelements, respectively, to prevent backing-out, the first and secondspring biased snapper elements being biased to the first position.

The height of the plate portion is preferably substantially equal to aheight of the spacer portion and a width of the plate portion ispreferably substantially equal to a width of the spacer portion. Thespacer portion preferably includes first and second recesses formed inthe first and second side surfaces thereof, respectively, and the plateportion preferably includes first and second projections extending fromthe plate portion for engaging the first and second recesses.

Each of the first and second spring biased snapper elements preferablyincludes a spring and a snapper element. The snapper element preferablyincluding a tapered first end that protrudes into the first and secondbone fixation holes for interacting with the first and second bonefixation elements, respectively, and a second end for interacting withthe spring. The first and second spring biased snapper elements arepreferably secured within the first and second boreholes, respectively,via first and second pins, respectively.

In use, insertion of the first and second bone fixation elementspreferably causes the first and second spring biased snapper elements tomove from their respective first position to their respective secondpositions. Insertion of the first and second bone fixation elementspreferably causes a head portion of the first and second bone fixationelements to contact the first and second spring biased snapper elements,respectively, to cause the first and second spring biased snapperelements to recoil from their first positions to the their secondpositions. Further insertion of the first and second bone fixationelements preferably causes the head portions of the first and secondbone fixation elements to move distally of the first and second springbiased snapper elements resulting in the first and second snapperelements automatically moving from their second position to their firstpositions.

The implant preferably also includes first and second stops to preventover insertion of the implant during implantation and to assist insecuring a position of the implant during insertion of the first andsecond bone fixation elements, the first stop extending superiorly ofthe top surface of the plate portion for contacting the superiorvertebral body, the second stop extending inferiorly of the bottomsurface of the plate portion for contacting the inferior vertebral body.The first and second stops are preferably integrally formed with theplate portion.

In another exemplary embodiment, the implant sized and adapted forinsertion into an intervertebral disc space between superior andinferior vertebral bodies includes (a) first and second bone fixationelements; (b) a spacer portion including a top surface for contactingthe superior vertebral body, a bottom surface for contacting theinferior vertebral body, a first side surface, a second side surface, aleading surface and a trailing surface; and (c) a plate portion coupledto the spacer portion. The plate portion includes a top surface, abottom surface, a first side surface, a second side surface, a leadingsurface, a trailing surface, and first and second bone fixation holes.The first and second bone fixation holes sized and adapted for receivingthe first and second bone fixation elements, respectively. The firstbone fixation hole is angled so that the first bone fixation elementengages the superior vertebral body and the second bone fixation hole isangled so that the second bone fixation element engages the inferiorvertebral body. The implant further including (d) a propeller elementhaving a longitudinal axis extending between a first end and a secondend. The propeller element being coupled to the plate portion in-betweenthe first and second bone fixation holes. The propeller being rotatablebetween a first position wherein the propeller does not interfere withfirst and second bone fixation holes so that the first and second bonefixation elements can be inserted into the first and second bonefixation holes, respectively, to a second position wherein the first endof the propeller at least partially covers at least a portion of thefirst bone fixation hole and the second end of the propeller at leastpartially covers at least a portion of the second bone fixation hole toprevent backing out of the first and second bone fixation elements onceimplanted. In the first position, the longitudinal axis of the propelleris preferably oriented generally parallel to an axis of the implant sothat the first end of the propeller extends superiorly of the topsurface of the plate portion and the second end of the propeller extendsinferiorly of the bottom surface of the plate portion so that thepropeller acts as a stop during implantation of the implant to preventover insertion of the implant and to assist in securing a position ofthe implant during insertion of the first and second bone fixationelements.

The propeller is preferably rotated through a range of about ninetydegrees (90°) from the first position to the second position. Thepropeller preferably includes a threaded screw for engaging a threadedborehole formed in the plate portion. The trailing surface of the plateportion preferably includes tapered recesses that form guide ramps forthe first and second ends of the propeller as the propeller is beingrotated from the first position to the second position and so that inthe second position, the propeller lies flush with the trailing surfaceof the plate portion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments of the application, will be better understood whenread in conjunction with the appended drawings. For the purposes ofillustrating the implant of the present application, there is shown inthe drawings preferred embodiments. It should be understood, however,that the application is not limited to the precise arrangements andinstrumentalities shown. In the drawings:

FIG. 1A illustrates an anterior perspective view of an implant accordingto a first preferred embodiment of the present application;

FIG. 1B illustrates a side elevational view of the implant of FIG. 1A;

FIG. 1C illustrates a top plan view of the implant of FIG. 1A;

FIG. 1D illustrates an anterior elevational view of the implant of FIG.1A;

FIG. 1E illustrates a cross-sectional view of the implant of FIG. 1A,taken along line 1E-1E of FIG. 1C;

FIG. 1F illustrates a cross-sectional view of the implant of FIG. 1A,taken along line 1F-1F of FIG. 1A;

FIG. 2A illustrates an anterior perspective view of a plate portion ofthe implant of FIG. 1A;

FIG. 2B illustrates a cross-sectional view of the plate portion of FIG.2A, taken along line 2B-2B of FIG. 2A;

FIG. 2C illustrates a magnified, cross-sectional view of a retentionmechanism used in connection with the implant of FIG. 1A;

FIG. 2D illustrates a perspective view of the retention mechanism ofFIG. 2C;

FIGS. 2E-2J illustrate various alternate views of the implant shown inFIG. 1A incorporating various alternate designs of a stop memberconfigured for embedding at least partially into the vertebral bodiesduring impaction;

FIG. 3A illustrates a top plan view of an exemplary removal instrumentfor contacting and recoiling the retention mechanism of FIG. 2D toenable removal of the bone fixation elements from the implant;

FIG. 3B illustrates a magnified, cross-sectional view of the removalinstrument of FIG. 3A, taken along line 3B-3B of FIG. 3A;

FIG. 4A illustrates an anterior perspective view of an implant accordingto a second preferred embodiment of the present application, theretention mechanism being in a first position;

FIG. 4B illustrates a side elevational view of the implant shown in FIG.4A, the retention mechanism being in the first position;

FIG. 4C illustrates an anterior perspective view of the implant shown inFIG. 4A, the retention mechanism being in a second position;

FIG. 4D illustrates a side elevational view of the implant shown in FIG.4A, the retention mechanism being in the second position;

FIG. 5A illustrates an anterior perspective view of the implant shown inFIG. 4A inserted into an intervertebral disc space between adjacentvertebral bodies, the retention mechanism being in the first positionwherein the retention mechanism acts as a stop preventing over-insertionof the implant into the disc space;

FIG. 5B illustrates an anterior perspective view of the implant shown inFIG. 4A inserted into an intervertebral disc space between adjacentvertebral bodies, the retention mechanism being in the second position;

FIG. 6A illustrates a top perspective view of the implant shown in FIG.4A, the plate portion incorporating an optional thread blockingmechanism;

FIG. 6B illustrates an alternate top perspective view of the implantshown in FIG. 6A illustrating the optional thread blocking mechanism incontact with an implanted bone fixation element;

FIG. 7A illustrates an anterior exploded perspective view of the plateportion used in connection with the implant of FIG. 4A, the retentionmechanism incorporating a second exemplary coupling mechanism forengaging the plate portion;

FIG. 7B illustrates a cross-section view of the plate portion andretention mechanism shown in FIG. 7A, taken along line 7B-7B of FIG. 7A;

FIG. 8 illustrates a partial cross-sectional view of a plate portionused in connection with the implant of FIG. 4A, the retention mechanismincorporating a third exemplary coupling mechanism for engaging theplate portion;

FIG. 9A illustrates an anterior perspective view of the implant shown inFIG. 4A, the implant incorporating a second exemplary spacer portion;

FIG. 9B illustrates a top perspective view of the implant shown in FIG.9A with an optional porous PEEK portion omitted;

FIG. 9C illustrates a cross-sectional view of the implant shown in FIG.9A, taken along line 9C-9C in FIG. 9A with the optional porous PEEKportion omitted;

FIGS. 10A-10E illustrate various views of an exemplary insertioninstrument and method for inserting the implant of FIG. 4A; and

FIGS. 11A-11C illustrate various views of an exemplary inserter anddrill guide instrument for inserting an implant.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inwardly” or “distally” and “outwardly” or “proximally” refer todirections toward and away from, respectively, the geometric center ofthe implant and related parts thereof. The words, “anterior”,“posterior”, “superior,” “inferior” and related words and/or phrasesdesignate preferred positions and orientations in the human body towhich reference is made and are not meant to be limiting. Theterminology includes the above-listed words, derivatives thereof andwords of similar import.

Similar reference numerals will be utilized throughout the applicationto describe similar or the same components of each of the preferredembodiments of the implant described herein and the descriptions willfocus on the specific features of the individual embodiments thatdistinguish the particular embodiment from the others.

Preferred embodiments of the present application are directed to animplant 10, 200 (“10-200”). It should be understood that while thevarious embodiments of the implant 10-200 will be described inconnection with spinal surgery, those skilled in the art will appreciatethat the implant 10-200, as well as the components thereof, may be usedfor implantation into other parts of the body, including, for example,long bones or bones in knee, hip, shoulder, or other joint replacementor for bone augmentation.

The various embodiments of the implant 10-200 are preferably sized andconfigured to be implanted between adjacent vertebral bodies V. Theimplant 10-200 may be sized and configured to replace all orsubstantially all of an intervertebral disc space D between adjacentvertebral bodies V or only part of the intervertebral disc space D. Inaddition, the preferred implant 10-200 may be configured to replace anentire vertebral body V and related disc spaces D or multiple discspaces D in a patient's spine, as would be apparent to one havingordinary skill in the art based upon a review of the presentapplication. The implant 10-200 may be adapted for use in the anterior,antero-lateral, direct lateral, extra-foraminal, transforaminal, andposterior approaches for insertion into the spine.

The implant 10-200 of each of the preferred embodiments includes aninterbody spacer portion 20, 220, 220′ (“20-220”) and a plate portion50, 250, 250′, 250″, 250′″ (“50-250”). The spacer portion 20-220 ispreferably sized and configured for implantation into the intervertebraldisc space D between adjacent vertebral bodies V. The spacer portion20-220 of each of the preferred embodiments includes a top surface 22, abottom surface 24, a first side surface 26, a second side surface 28, aleading surface 30 and a trailing surface 32. The top and bottomsurfaces 22, 24 are suitable for contacting and are adapted for beingsecured relative to the end plates of adjacent vertebral bodies V. Thespacer portion 20-220 is preferably sized and configured to maintainand/or restore a desired intervertebral disc height between the adjacentvertebral bodies V. Accordingly, the top and bottom surfaces 22, 24 mayinclude a series of teeth, ridges, spikes or other similar projections25 to aid in securing the implant 10-200 to the endplates of theadjacent vertebral bodies V.

The top and bottom surfaces 22, 24 may also include a curved or atapered surface to help provide an anatomical shape for mating with thepatient's spine or to orient the endplates of the adjacent vertebralbodies V in a desired manner. The particular surface shape andcurvature, taper or alternate surface feature in the anterior-posteriordirection, as well as the particular surface shape and curvature, taperor alternate surface feature in the medial-lateral direction will dependupon the location where the implant 10-200 is intended to be implantedand/or surgeon preferences or whether the implant 10-200 is utilized inanother area in the body.

The spacer portion 20-220 may also include one or more boreholes,openings, windows or channels 34 for receiving bone graft material. Forexample, the implant 10-200 may include one or more vertical openings,windows or channels extending through the spacer portion 20-220 from thetop surface 22 to the bottom surface 24 for insertion of bone graftmaterial, such that bone growth is promoted through the verticalopenings, windows or channels 34 following implantation of the implant10-200. One or more boreholes, openings, windows or channels 34 isespecially preferred if the spacer portion 20-220 is constructed of anon-allograft or non-bone-growth material, such as Polyetheretherketone(“PEEK”).

The plate portion 50-250 is preferably coupled to the spacer portion20-220 to provide increased implant stability during healing as well asto optimally orient the trajectory of bone fixation elements 70 duringimplantation.

The plate portion 50-250 of each of the preferred embodiments includes atop surface 52, a bottom surface 54, a first side surface 56, a secondside surface 58, a leading surface 60 and a trailing surface 62. Theplate portion 50-250 preferably contacts the trailing surface 32 of thespacer portion 20-220 and preferably does not extend beyond or does notincrease greatly the vertical or lateral perimeter of the spacer portion20-220. In this manner, the implant 10-200 has a low profile.Additionally, in this manner, the plate portion 50-250 is preferablyentirely implanted within the intervertebral disc space D between theadjacent vertebral bodies V such that the plate portion 50-250 haslittle or no external profile (e.g., the plate portion 50-250 does notextend anterior beyond an edge of the disc space D). In this manner,little or no structure protrudes outside of the bounds of the disc spaceD or the profile of the vertebral bodies V, thereby limiting dysphasiaand patient discomfort. In use, the plate portion 50-250 may be sizedand configured so that the top and bottom surfaces 52, 54 of the plateportion 50-250 contact the endplates of the adjacent vertebral bodies V.Alternatively, the plate portion 50-250 may be sized and configured sothat only the spacer portion 20-220 contacts the adjacent vertebralbodies V. For example, the height of the plate portion 50-250 may besmall enough so that it does not contact the vertebral bodies V whenconnected to the spacer portion 20-220 in an implanted position.

The plate portion 50-250 may be coupled to the spacer portion 20-220 byany coupling mechanism now or hereafter known. For example, the spacerportion 20-220 may include one or more recesses 36 formed in the side ortrailing surfaces for engaging one or more projections 64 extending fromthe plate portion 50-250. Preferably the spacer portion 20 includes arecess 36 formed in each of the side surfaces 26, 28 thereof forengaging projections 64 extending from the plate portion 50-250. Therecesses 36 may extend completely from the top surface 22 to the bottomsurface of the spacer portion 20 or may extend only partially fromeither the top or bottom surface 20, 22. Other coupling mechanisms forcoupling the plate portion 50-250 to the spacer portion 20-220 aredisclosed in International Application No. PCT/US2008/082473 filed onNov. 5, 2008 and entitled, “Low Profile Intervertebral Implant”, thecontents of which are hereby incorporated by reference in theirentirety.

The trailing surface 62 of the plate portion 50-250 preferably includesa tool engagement feature 80 for engaging one or more insertion tools.The tool engagement feature 80 may be in any form now or hereafter knownfor such purpose including one or more recesses formed in the trailingsurface 62 of the plate portion 50-250, the recesses extending from topand bottom surfaces 52, 54, respectively, for engaging arms of theinsertion tool. Alternatively, the tool engagement feature 80 may be athreaded bore (not shown) formed in the trailing surface 62 of the plateportion 50-250 for engaging a threaded stem extending from the insertiontool, etc.

The implant 10-200 preferably includes one or more bone fixation holes40 for receiving one or more bone fixation elements 70, preferably bonescrews so that, in use, after the implant 10-200 has been inserted intothe intervertebral disc space D between adjacent vertebral bodies V, theimplant 10-200 may be secured to the adjacent vertebral bodies V. Thebone fixation elements 70 preferably include a threaded shaft 72 and apartially spherical head portion 74 that is generally smooth where itcontacts the bone fixation hole 40. The threaded shaft 72 may beself-drilling, i.e. does not necessitate the drilling of pilot holes,but are not so limited. The bone fixation elements 70 are not limited tobone screws 70 and may be comprised of a helical nail, a distallyexpanding nail or screw, etc. The bone fixation holes 40 are preferablysized and configured so that the head portion 74 of the bone fixationelements 70 do not protrude proximally beyond the trailing surface 62 ofthe plate portion 50, when the bone fixation elements 70 have been fullyimplanted.

The bone fixation holes 40 preferably include a curved orfrusta-spherical surface for contacting an underside of the generallysmooth or frusta-spherical surface of the head portion 74 of the bonefixation elements 70 so that the bone fixation elements 70 canpolyaxially rotate with respect to the plate portion 50-250 and avariety of trajectory angles can be chosen for the bone fixationelements 70 according to surgeons' preferences or needs as well as toenable the implant 10-200 to settle during healing.

The plate portion 50-250 preferably includes first and second bonefixation holes 40 for receiving first and second bone fixation elements70 with the first bone fixation element 70 being angled upwardly forengaging the superior vertebral body V and the second bone fixationelement 70 being angled downwardly for engaging the inferior vertebralbody V. That is, the bone fixation holes 40 preferably have alongitudinal axis 41 that is oriented obliquely with respect to theimplant 10-200 so that the bone fixation elements 70 form a fastenerangle with respect to the top and bottom surfaces 22, 24 of the spacerportion 20 wherein bone fixation angle may be in the range betweentwenty degrees (20°) and sixty degrees (60°), and more preferablybetween thirty degrees (30°) and fifty degrees (50°). The bone fixationangle may be the same for all of the holes 40 or may be different foreach of the holes 40. In addition, the bone fixation holes 40 may bedirected inwardly toward the center of the implant 10-200 or outwardlyaway from the center of the implant 10-200, preferably at a lateral bonefixation angle α so that the bone fixation elements 70 extend laterallyinward toward a center plane of the implant 10-200 or laterally outwardaway from the center plane of the implant 10-200. The lateral bonefixation angle α may be in the range between plus sixty degrees (60°)and minus sixty degrees (−60°), preferably between zero degrees (0°) andplus or minus thirty degrees (30°), and more preferably about plus orminus fifteen degrees (15°). The lateral bone fixation angle α may bethe same for all holes 40 or may be different for each hole 40. However,as would be understood by one of ordinary skill in the art based upon areading of this disclosure, a plurality of potential angles is possiblesince the bone fixation elements 70 are polyaxial, as will be describedin greater detail below.

It should be understood however that the implant 10-200 may includethree, four, five or more bone fixation holes 40 configured to receive acorresponding number of bone fixation elements 70 in any number ofconfigurations. In addition, the number of bone fixation elements 70extending from the top and bottom surfaces 22, 24 may be varied and thenumber of bone fixation elements 70 extending from the top surface 22need not equal the number of bone fixation elements 70 extending fromthe bottom surface 24.

Exit openings for the bone fixation holes 40 preferably are formed atleast partially in the top or bottom surfaces 52, 54 of the plateportion 50-250. The exit openings may also be formed at least partiallyor entirely in the top or bottom surfaces 22, 24 of the spacer portion20-220. The bone fixation holes 40 may also include a partiallyspherical interior volume to accommodate the partially sphericalgeometry of the head portion 74 of the bone fixation elements 70 toenable a range of polyaxial orientations to be chosen for the bonefixation elements 70 with respect to the vertebral bodies V.

The implant 10-200 preferably also includes a retention mechanism forreducing the likelihood that the bone fixation elements 70 maypostoperatively uncouple from the implant 10-200 and migrate from thedisc space D. In use, the retention mechanism preferably covers at leasta portion of the bone fixation holes 40 and hence the bone fixationelements 70 to prevent the bone fixation elements 70 from backing-out,as will be described in greater detail below.

The implant 10-200 including the spacer portion 20-220 and the plateportion 50-250 may be constructed of any suitable biocompatible materialor combination of materials including, but not limited to one or more ofthe following metals such as titanium, titanium alloys, stainless steel,aluminum, aluminum alloy, magnesium, etc., polymers such as, PEEK,porous PEEK, carbon fiber PEEK, resorbable polymers, PLLA, etc.,allograft, synthetic allograft substitute, ceramics in the form ofbioglass, tantalum, Nitinol, or alternative bone growth material or somecomposite material or combination of these materials.

The spacer portion 20-220 may be formed of a different material than theplate portion 50-250. For example, the plate portion 50-250 may beformed of a metallic material such as, a titanium or a titanium alloy,and the spacer portion 20-220 may be formed of a non-metallic materialsuch as, a polymer such as, PEEK, an allograft, a bioresorbablematerial, a ceramic, etc. Alternatively, the plate portion 50-250 andthe spacer portion 20-220 may be formed from the same material. Inaddition, the plate portion 50-250 and spacer portion 20-220 may beintegrally formed, pre-assembled or separately provided to a surgeon andassembled in the operating room.

As will be appreciated by one of ordinary skill in the art, the implant10-200, or portions thereof, may also be coated with various compoundsto increase bony on-growth or bony in-growth, to promote healing or toallow for revision of the implant 10-200, including hydroxyapatite,titanium-nickel, vapor plasma spray deposition of titanium, or plasmatreatment to make the surface hydrophilic.

Referring to FIGS. 1A-2J, the intervertebral implant 10 of a firstpreferred embodiment includes the spacer portion 20, the plate portion50, first and second bone fixation elements 70 and the retentionmechanism. In the first preferred embodiment, the retention mechanism isin the form of a spring biased snapper element 110. More preferably, theplate portion 50 includes a borehole 112 in communication with each ofthe bone fixation holes 40 for receiving a spring 114 and a snapperelement 116. The borehole 112 defines a longitudinal axis thatintersects the longitudinal axis 41 of the bone fixation hole 40 andhence the bone fixation element 70. The intersection angle may betransverse, perpendicular or acute.

The snapper 116 preferably includes a first end 118 for contacting orinteracting with the head portion 74 of the bone fixation element 70 anda second end 120 for receiving, contacting or interacting with thespring 114. The spring 114 is preferably sized and configured to biasthe snapper 116 so that the snapper 116 protrudes into the bone fixationhole 40 and over the head portion 74 of the bone fixation element 70,once the bone fixation element 70 has been inserted into the bonefixation hole 40 to prevent back-out. The spring-biased snapper 116 ispreferably secured within the borehole 112 via a pin or set screw 125.That is, the snapper 116 may include a groove or a recess 126 formedtherein for mating with a pin or set screw 125, which is located withina borehole 125 a. The interaction of the pin or set screw 125 and thegroove or recess 126 preventing the snapper 116 from falling out of theborehole 112. For example, the snapper 116 preferably includes a roundedmilled slot 126 and the pin or set screw 125 may be threaded andpreferably includes a form fit so that the snapper 116 may be receivedand caught inside of the slot 126 formed in the snapper 116. Othermechanism for securing the spring-biased snapper 116 to the plateportion 50 may be used.

In the first preferred embodiment, the plate portion 50 also includesfirst and second stops 65, wherein the first stop 65 protrudessuperiorly from the top surface 52 of the plate portion 50 forcontacting the superior vertebral body V and the second stop 65protrudes inferiorly from the bottom surface 54 of the plate portion 50for contacting the inferior vertebral body V. Incorporation of more orless stops 65 is envisioned. Incorporation of the first and second stops65 facilitates fully seating the implant 10 with respect to the adjacentvertebral bodies V regardless of the irregular anatomy of a patient'sspine, which often characterizes the outer surface of the vertebralbodies V. The stops 65 are preferably integrally formed on the plateportion 50.

In use, the stops 65 are configured to abut the anterior aspects of thevertebral bodies V during implantation, although the stops 65 may abutthe lateral or antero-lateral aspects of the vertebral bodies Vdepending upon the surgical procedure and insertion path being utilized.The stops 65 assist in preventing over-insertion of the implant 10during implantation and assist in securing the position of the implant10 during insertion of the bone fixation elements 70, as will bedescribed in greater detail below. In part, due to the disposition ofthe stops 65, the implant 10 generally has a zero-profile external tothe disc space D at least along a cranial-caudal midline, because thetrailing surface 62 of the plate portion 50 can be designed to be convexto match the disc space D. Referring to FIGS. 2E-2J, a distal surface 65a of the stops 65 can be configured to embed at least partially into thevertebral bodies V during impaction to further reduce the profile of theplate portion 50 exterior to the disc space D, if so desired. Forexample, as shown in FIG. 2E, the distal surface 65 a of the stops 65may include a pyramid shaped projection or tooth 66 extending therefromfor embedding at least partially into the vertebral bodies V duringimpaction. Alternatively, the distal surface 65 a of the stops 65 mayinclude a plurality of projections or teeth 67 (as shown in FIG. 2F), avertical blade type projection 68 (as shown in FIGS. 2G and 2H) or atransverse blade type projection 69 (as shown in FIGS. 2I and 2J)extending therefrom for embedding at least partially into the vertebralbodies V during impaction.

In operation, a surgeon prepares a pathway or channel to the disc spaceD, performs at least a partial discectomy, and inserts the implant 10including the spacer portion 20 and the plate portion 50 into the discspace D until the stops 65 contact the adjacent vertebral bodes V. Afterthe surgeon has chosen a desirable entry angle for the bone fixationelements 70, the surgeon advances the first and second bone fixationelements 70 into and through the bone fixation holes 40 at the selectedangle, with or without the prior formation of pilot holes. Advancementof the bone fixation elements 70 into the bone fixation holes 40 causesthe head portion 74 of the bone fixation elements 70 to contact theinner spherical portions of the bone fixation holes 40 and tends to drawthe vertebral bodies V into alignment as opposed to resulting in theover-insertion of the implant 100 since the stops 65 guide the movementof the vertebral bodies V during bone fixation manipulation. That is,because the stops 65 contact the adjacent vertebral bodies V andprevents over-insertion of the implant 10 into the disc space D,advancement of the bone fixation elements 70 tends to pull and/orreposition the adjacent vertebral bodies V together to promote fusion.The bone fixation elements 70 are advanced until the vertebral bodies Vare optimally aligned and the head portions 74 of the bone fixationelements 70 are advanced into the spherical portions of the bonefixation holes 70.

As the bone fixation elements 70 advance through the bone fixation holes40, the underside of the head portion 74 of the bone fixation elements70 contact the first end 118, preferably a tapered end portion 117, ofthe snapper elements 116 that protrude into the bone fixation holes 40,thereby urging the snapper elements 116 to recoil upon the spring 114and retracting the snapper elements 116 from the bone fixation holes 40so that the bone fixation elements 70 can be implanted. Once the headportions 74 of the bone fixation elements 70 advance past the taperedend portion 117 of the snapper elements 116, the spring 114 forces thesnapper elements 116 back to their initial position in which the snapperelements 116 protrude at least partially into the bone fixation holes40. In this position, the first end 118 of the snapper element 116 isdesigned to cover at least a portion, contact and/or interact with thetop surface of the head portions 74 of the bone fixation elements 70 toblock the head portions 74 of the bone fixation elements 70 and limitthe bone fixation elements 70 from backing-out of the bone fixationholes 40. Specifically, the first end 118 of the snapper element 110preferably extends into the bone fixation hole 40 such that the headportion 74 of the bone fixation element 70 is unable to move out of thebone fixation hole 40 without impacting the first end 118.

Post implantation, the bone fixation elements 70 are preferably free totoggle to allow for settling during postoperative healing. Referring toFIGS. 3A and 3B, if a surgeon decides the placement of the implant 10 isnot optimal, adjustments can be made by compressing the snapper elements116 with a blunt instrument or a sleeve thereby allowing the bonefixation elements 70 to be removed. For example, a removal instrument1000 may include an inner shaft 1010 for engaging the bone fixationelement 70 and an outer shaft 1020 for contacting and recoiling thesnapper element 116 so that the bone fixation element 70 may be removedfrom the plate portion 50.

Referring to FIGS. 4A-5B, the intervertebral implant 200 of a secondpreferred embodiment includes the interbody spacer portion 220, theplate portion 250, first and second bone fixation elements 70 and theretention mechanism. In the second preferred embodiment, the retentionmechanism is in the form of a propeller 310 moveable, more preferablyrotatable, between a first position (illustrated in FIGS. 4A, 4B and 5A)and a second position (illustrated in FIGS. 4C, 4D and 5B). In the firstposition, the propeller 310 does not interfere with first and secondbone fixation holes 40 so that the first and second bone fixationelements 70 can be inserted into the adjacent vertebral bodies V. In thesecond position, the propeller 310 blocks or covers at least a portionof the bone fixation holes 40 and hence at least a portion of theimplanted bone fixation elements 70 to prevent backing-out.

The propeller 310 is preferably preassembled or pre-attached to theplate portion 250. The propeller 310 may be attached to the plateportion 250 by any coupling mechanism now or hereafter known in the artincluding those described below. In the second preferred embodiment, thepropeller 310 is preassembled to the plate portion 250 via a retainingscrew 320 that interfaces with a threaded borehole (not shown) disposedbetween the bone fixation holes 40 formed in the plate portion 250. Theretaining screw 320 may extend into and be threadably coupled to thespacer portion 220, but is not so limited. Alternatively, the retainingscrew 320 may be securely coupled with respect to the plate portion 250by a cross-pinned shaft, a rivet, a helical wedge attached to the shaftof the retaining screw 320, etc. The propeller 310 includes first andsecond ends 312, 314 defining a longitudinal axis that is generallytransverse to the longitudinal axis of the retaining screw 320.

The propeller 310 and the retaining screw 320 are preferably rotatablethrough a range of about ninety degrees (90°) from the first position tothe second position. In the first position, the longitudinal axis of thepropeller 310 is oriented generally parallel to a longitudinal axis ofthe implant 200 and generally parallel to the cranial-caudal axis of thespine so that the propeller 310 does not interfere with the bonefixation holes 40 or bone fixation elements 70 to enable insertion ofthe bone fixation elements 70 into the adjacent vertebral bodies V. Inthe second position, the longitudinal axis of the propeller 310 isgenerally oriented perpendicular to the cranial-caudal axis of the spineso that the propeller 310 blocks or covers at least a portion of thebone fixation holes 40 and the bone fixation elements 70 to preventbacking-out. That is, in the second position, the propeller 310 coversat least a portion of the head portion 74 of the bone fixation elements70 while in the first position, the propeller 310 permits insertion ofthe bone fixation elements 70 into the bone fixation holes 40 and intothe adjacent vertebral bodies V.

The retaining screw 320 preferably includes an engagement feature 321for engaging an insertion instrument 500, as will be described ingreater detail below, to rotate the retaining screw 320 and thepropeller 310 to and between the first and second positions. Theretaining screw 320 and the propeller 310 are coupled to one another andpreferably rotate together via a two point interference fit between theouter diameter of the retaining screw 320 and the diameter of acounterbore (not shown) through the propeller 310.

The plate portion 250 preferably includes a tapered recess 330 thatforms a guide ramp so that in the second position, the propeller 310preferably lies flush with the trailing surface 62 of the plate portion250 (as best shown in FIG. 4D). Accordingly, in the first position(FIGS. 4A and 4B), the propeller 310 extends from the trailing surface62 of the plate portion 250 and in the second position (FIGS. 4C and4D), the anterior surface of the propeller 310 lies generally flush orsomewhat recessed with respect to the trailing surface 62. Therefore, inan implanted configuration when the propeller 310 is in the secondposition, the entire implant 200, including the propeller 310, lieswithin the bounds of the patient's spine or posteriorly relative to theanterior aspect of the vertebrae V.

In operation, a surgeon prepares a pathway or channel to the disc spaceD, performs at least a partial discectomy, and inserts the implant 200including the spacer portion 220 and the plate portion 250 into the discspace D with the propeller 310 in the first position. In the firstposition, the propeller 310 is sized to act as a stop duringimplantation of the implant 200 to prevent over-insertion of the implant200, as well as to secure the position of the implant 200 during theinsertion of the bone fixation elements 70. Specifically, the ends 312,314 of the propeller 310 contact and/or engage the adjacent vertebralbodies V to mechanically block further insertion of the implant 200 intothe disc space D (as best shown in FIG. 5A).

After the surgeon has chosen a desirable entry angle for the bonefixation elements 70, the surgeon advances the first and second bonefixation elements 70 into and through the bone fixation holes 40 at theselected angle, with or without the prior formation of pilot holes.Advancement of the bone fixation elements 70 into the bone fixationholes 40 causes the head portion 74 of the bone fixation elements 70 tocontact the inner spherical portions of the bone fixation holes 40 andtends to draw the vertebral bodies V into alignment as opposed toresulting in the over-insertion of the implant 200 since the propeller310 preferably guides the movement of the vertebral bodies V during bonefixation manipulation. The bone fixation elements 70 are advanced untilthe vertebral bodies V are optimally aligned and the head portions 74 ofthe bone fixation elements 70 are advanced into the spherical portionsof the bone fixation holes 70. The retaining screw 320 and the propeller310 are then rotated ninety degrees (90°) from the first position to thesecond position, guided by the recesses 330 formed in the trailingsurface 62 of the plate portion 250, by mating an insertion instrumentto the instrument engagement feature 321 on the retaining screw 320. Asthe retaining screw 320 is rotated from the first position to the secondposition, the retaining screw 320 preferably advances distally, based onthe pitch of the threading formed on its shaft, and the propeller 310rotates down the guide ramp formed by the recesses 330 and comes to resttherein while overlying the head portions 74 of the bone fixationelements 70. The shape of the guide ramp formed by the recesses 330preferably stops the propeller 310 from over rotating past the secondposition, such that the ends of the propeller 310 at least partiallycover the head portions 74 of the bone fixation elements 70. As such,the bone fixation elements 70 are prevented from backing-out of theplate portion 250 and the spacer portion 220 by the propeller 310.

Post implantation, the bone fixation elements 70 are preferably free totoggle to allow for settling during postoperative healing. If a surgeondecides the placement of the implant 200 is not optimal, adjustments canbe made by rotating the propeller 310 back to the first position,thereby unblocking the head portions 74 of the bone fixation elements 70and allowing adjustments thereto.

Referring to FIGS. 6A and 6B, a second preferred embodiment of the plateportion 250′ for use with implant 200 is illustrated. In the secondpreferred embodiment of the plate portion 250′, the bone fixation holes40 include a protruding thread blocking mechanism 350 that is sized andconfigured to permit the threaded advancement of the first and secondbone fixation elements 70 with respect to the bone fixation holes 40until the proximal most thread 73 formed on the shaft 72 of the bonefixation element 70 advances distally past the thread blocking mechanism350, at which point the distal surface of the thread blocking mechanism350 contacts a proximal side of the proximal most thread 73 to inhibitthe first and second bone fixation elements 70 from backing-out of thebone fixation holes 40. The thread blocking mechanism 350 may assume theform of a raised ridge or interrupted ring of material or a variety ofother protruding features configured to allow the proximal most thread73 of the bone fixation element 70 to advance to a point from whichretreat in the opposite direction is inhibited. Alternatively, thethread blocking mechanism 350 can be disposed within the bone fixationholes 40 to block the proximal surface of the head portions 74 of thebone fixation elements 70, as opposed to the proximal most threads 73.Alternatively, the thread blocking mechanism 350 can be configured toengage a corresponding indentation (not shown) formed on the sides ofthe head portions 74 of the bone fixation elements 70.

The bone fixation elements 70 may further include an undercut 75 betweenthe proximal most thread 73 and the distal portion of the head portion74 for enabling the bone fixation element 70 to generally rotate freelyafter being fully seated in the bone fixation hole 40 to thereby permitlagging of the vertebral bodies V with respect to the implant 200 duringimplantation.

In operation, the implant 200 is positioned between the adjacentvertebral bodies V and the bone fixation elements 70 are advanced intothe bone fixation holes 40 until the proximal most thread 73 formed onthe shaft portion 72 of the bone fixation elements 70 advance past theprotruding thread blocking mechanism 350. The bone fixation elements 70are fully seated with respect to the plate portion 250′ in thisposition. The distal surface of the thread blocking mechanism 350contacts the proximal side of the proximal most thread 73 formed on theshaft portions 72 of the bone fixation elements 70 to limit the bonefixation elements 70 from backing-out of the bone fixation holes 40. Thebone fixation elements 70 are generally free to rotate after being fullyseated due to the inclusion of the undercuts 75 between the proximalmost thread 73 and the head portion 74 of each bone fixation elements 70to permit lagging of the vertebral bodies V with respect to the implant200 during implantation. The propeller 310 can then be utilized inconjunction with the thread blocking mechanism 350 to secure theposition of the implant 200 during the insertion of the bone fixationelements 270, as well as to add additional back-out prevention.Alternatively, it is envisioned that the thread blocking mechanism 350can be incorporated into the first preferred embodiment of the implant10.

Referring to FIGS. 7A and 7B, a third preferred embodiment of the plateportion 250″ for use with the implant 200 is illustrated. The thirdpreferred embodiment of the plate portion 250″ includes an alternatecoupling mechanism for coupling the propeller 310″ to the plate portion250″. In this embodiment, the propeller 310″ includes a plurality ofslots 317″ extending from a distal end 316″ of the propeller 310″ sothat the propeller 310″ includes a plurality of spring-like fingers 315″oriented along an axis that extends distally, generally perpendicular tothe longitudinal axis of the ends 312″, 314″ of the propeller 310″. Thespring fingers 315″ preferably include an outwardly extending flange318″ at the distal end 316″ thereof. The plate portion 250″ preferablyincludes a non-threaded borehole 263″ disposed between the bone fixationholes 40. The non-threaded borehole 263″ preferably includes one or moreramps 263 a″ and one or more steps 263 b″ for interfacing with thespring fingers 315″ for securing the propeller 310″ to the plate portion250″.

An optional retaining clip 340″, such as a wishbone clip formed of, forexample, elgiloy, may be mounted in the borehole 263″ to further assistin securing the propeller 310″ to the plate portion 250″ by allowinginsertion of the propeller 310″ into the borehole 263″ while providingadditional protection against the propeller 310″ from backing-out of theborehole 263″.

In operation, the propeller 310″ is assembled to the plate portion 250″by inserting the spring fingers 315″ into the borehole 263″ until thepropeller 310″ snaps into the borehole 263″, retaining the propeller310″ therein. That is, as the spring fingers 315″ advance into theborehole 263″, the tapered flanges 318″ formed on the distal end 316″ ofthe propeller 310″ and the spring fingers 315″ compress so that thefingers 315″ pass through the optional retaining clip 340″ after whichthe spring fingers 315″ partially spring back outwardly. The retainingclip 340″ may additionally flex slightly outwardly as the flange 318″passes therethrough, after which the retaining clip 340″ springs back toits initial configuration. As the spring fingers 315″ continue toadvance into the borehole 263″, the fingers 315″ pass over the step 263b″ and subsequently flex outwardly to their non-deflected configurationadjacent the ramp 263 a″. In this manner, the propeller 310″ isprevented from backing-out through the borehole 263″ via interactionbetween the flanges 318″ and the step 263 b″.

Referring to FIG. 8, a fourth preferred embodiment of the plate portion250′″ for use with the implant 200 is illustrated. The fourth preferredembodiment of the plate portion 250′″ includes a third alternatecoupling mechanism for coupling the propeller 310′″ to the plate portion250′″. In this embodiment, the non-threaded borehole 263′″ includes afirst ramp 263 a′″, a first step 263 b′″, a second preferred helicalramp 263 c′″, and a second step 263 d″″ as one moves from the trailingsurface 62 of the plate portion 250′″. The configuration of thepropeller 310′″ is substantially identical to the propeller 310″ of thesecond exemplary coupling mechanism described above.

In operation, the propeller 310′″ is assembled to the plate portion250′″ by inserting the spring fingers 315′″ into the non-threadedborehole 263′″ until the propeller 310′″ snaps into the borehole 263′″,which retains the propeller 310′″ therein. As the spring fingers 315′″advance into the borehole 263′″, the spring fingers 315′″ compress asthe tapered flanges 318′″ pass along the first ramp 263 a′″ and over thefirst step 263 b′″, at which point the spring fingers 315′″ and theflanges 318′″ partially spring outwardly thereby securing the propeller310′″ to the plate portion 250′″. The propeller 310′″ is prevented frombacking-out through the borehole 263′″ via interaction between theflanges 318′″ and the first step 263 a′″. In addition, as the propeller310′″ is moved from the first position to the second position, thespring fingers 315′″ further advance into the borehole 263′″, whereinthe flange 318′″ is guided by the preferred helically formed second ramp263 c′″, until the flange 318′″ passes over the second step 263 d′″. Thespring fingers 315′″ and the flanges 318′″ flex outwardly into theirnon-deflected configuration to block the propeller 310′″ frombacking-out through the borehole 263′″ via interaction between theflanges 318′″ and the second step 263 d′″.

Referring to FIGS. 9A-9C, an alternate embodiment of the spacer portion220′ for use with the first and second preferred embodiments of theintervertebral implant 10-200 (second preferred embodiment illustrated)includes a centralized porous PEEK region 422 concentrically surroundedby a conventional PEEK portion 420.

In operation, the implant 200 is implanted and secured within the discspace D in a similar manner as previously described. The central porousPEEK portion 422 of the spacer portion 220′ has a porosity that providesa suitable pathway through which blood is able to flow and bone is ableto grow to assist in promoting fusion with and between the adjacentvertebral bodies V. The porous PEEK portion 422 may extend from the topsurface 22 to the bottom surface 24 of the spacer portion 220′.Alternatively, the spacer portion 220′ may include a bridge 424. Whenthe spacer portion 220′ includes the bridge 424, first and second blindboreholes 426, 428 preferably extend from the top and bottom surfaces22, 24, respectively, to the bridge 424. The blind boreholes 426, 428may include tapered sidewalls 430 such that a diameter of the blindboreholes 426, 428 increases toward the center of the spacer portion220′. The bridge 424 may be formed of the same material as the rest ofthe spacer portion 220′, but is preferably constructed of porous PEEK.Alternately, the bridge 424 may be removable, e.g., capable of beingpopped out of the spacer portion 220′ to provide an axial throughbore.In operation, the blind boreholes 426, 428 are preferably filled withbone graft or other fusion promoting material and the implant 200′ isimplanted into the disc space D between the adjacent vertebral bodies V.The optional tapered sidewalls 430 of the blind bores 426, 428facilitate securing the position of the implant 200′ within the discspace D as fusion occurs into the blind boreholes 426, 428.

Referring to FIGS. 10A-10E, an exemplary insertion instrument 500 andmethod for inserting the implant 200 will now be described. Inconnection with the exemplary method, the propeller 310 will bedescribed and illustrated as unattached to the plate portion 250.However the exemplary method can be easily adapted to operate with thepropeller 310 pre-attached to the plate portion 250 or adapted tooperate with the first preferred embodiment of the implant 10, as wouldbe apparent to one having ordinary skill in the art based upon a reviewof the present application.

The insertion instrument 500 is configured to couple to the propeller310, to couple to the plate portion 250, to insert the implant 200 atleast partially into the disc space D, to permit insertion of the bonefixation elements 70 into the bone fixation holes 40, to secure thepropeller 310 to the plate portion 250, if necessary, and to rotate thepropeller 310 from the first position to the second position, ifnecessary.

The insertion instrument 500 preferably includes an inner shaft 520 andan outer tubular member 530. The inner shaft 520 preferably includes adistal engagement feature 525, such as a star drive, for interfacingwith the engagement feature 321 formed on the retaining screw 320. Theouter tubular member 530 preferably includes a distal engagement feature535 for interfacing with a corresponding engagement feature (not shown)formed on the plate portion 250. Accordingly, the instrument 500 retainsthe propeller 310 by securing the engagement feature 525 formed on theinner shaft 520 of the instrument 500 to the propeller 310. Theinstrument 500 retains the implant 200 by grasping the plate portion 250with the engagement feature 535 formed on the outer tubular member 530.

The inner shaft 520 is configured to translate within the outer tubularmember 530 along a longitudinal axis 501 of the instrument 500.Accordingly, the inner shaft 520, and hence the propeller 310, may betranslated proximally with respect to the outer tubular member 530, andhence with respect to the implant 200. For embodiments where thepropeller 310 is unattached to the plate portion 250 and where the plateportion 250 does not include one or more stops, the instrument 500 mayalso include one or more stops (not shown) to prevent over-insertion ofthe implant 200 into the disc space D as well as to secure the positionof the implant 200 with respect to the disc space D during theimplantation of the bone fixation elements 70.

In operation, the surgeon inserts the implant 200 into the disc space Dby using the instrument 500 to advance the implant 200 into the discspace D between the adjacent vertebral bodies V until one or more stops(not shown) abut the anterior (or lateral or antero-lateral) aspects ofthe vertebral bodies V. The bone fixation elements 70 are then insertedthrough the bone fixation holes 40 and into the vertebral bodies V whilelagging of the implant 200 is limited by the interaction of the stopswith the vertebral bodies V.

If unattached, the propeller 310 and the retaining screw 320 may then beadvanced into a corresponding borehole 263 formed in the plate portion250 by translating the inner shaft 520 distally with respect to theouter tubular member 530. The inner shaft 250 is then rotated so thatthe propeller 310 moves from its first position to its second positionto prevent back-out of the implanted bone fixation elements 70. Theinstrument 500 is then decoupled from the propeller 310 and theretaining screw 320.

Referring to FIGS. 11A-11C, an optional inserter and drill guideinstrument 600 can be utilized to insert any of the previously describedimplants 10-200 and to align the trajectory of an awl, drill, driverinstrument, etc. for pilot hole formation and/or bone fixation elementinsertion. The inserter and drill guide instrument 600 includes a pairof arms 610, 615 extending from a pair of handles 620, 625 that arecoupled at a pivot point 630. The arms 610, 615 include aiming barrels612, 616 at their distal ends, respectively, for aligning the trajectoryof the awl, drill, bone fixation elements, etc. The barrels 612, 616include guide ribs 613, 617, respectively, disposed on their outersurface for interfacing with a key 625 formed in the bone fixation holes40 of the implant 200. The interfacing guide ribs 613, 617 and keys 625are configured to limit rotation of the implant 10-200 relative to theinstrument 600, a feature that is especially preferred for implants10-200 having only two bone fixation holes 40.

In operation, the arms 610, 615 of the inserter and drill guideinstrument 600 are opened by squeezing the handles 620, 625 together andthe barrels 612, 616 are inserted into the bone fixation holes 40 formedin the plate portion 250 such that the guide ribs 613, 617 interfacewith the keys 625. Upon secure grasping of the implant 10-200, the arms610, 615 are locked into place and the instrument 600 may be used toinsert the implant 10-200 into an at least partially cleared out discspace D between the vertebral bodies V. The barrels 612, 616 can then beused to align the trajectory of an awl, drill, etc. to form pilot holesfor the bone fixation elements 70 or may align the trajectory of thebone fixation elements 70 in the case where self-drilling bone fixationelements 70 are utilized. Subsequent to the implantation of the bonefixation elements 70, the arms 610, 615 are unlocked and the inserterand drill guide instrument 600 is decoupled from the implant assembly.

While the foregoing description and drawings represent the preferredembodiments of the present invention, it will be understood that variousadditions, modifications, combinations and/or substitutions may be madetherein without departing from the spirit and scope of the presentinvention as defined in the accompanying claims. In particular, it willbe clear to those skilled in the art that the present invention may beembodied in other specific forms, structures, arrangements, proportions,and with other elements, materials, and components, without departingfrom the spirit or essential characteristics thereof. One skilled in theart will appreciate that the invention may be used with manymodifications of structure, arrangement, proportions, materials, andcomponents and otherwise, used in the practice of the invention, whichare particularly adapted to specific environments and operativerequirements without departing from the principles of the presentinvention. In addition, features described herein may be used singularlyor in combination with other features. The presently disclosedembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims, and not limited to the foregoingdescription.

1. (canceled)
 2. An intervertebral implant comprising: a spacer portiondefining a spacer trailing surface, a spacer leading surface oppositethe spacer trailing surface, a first side surface, a second side surfaceopposite the first side surface, and an inner surface, the inner surfaceincluding a first portion that is opposite the first side surface, asecond portion that is opposite the spacer leading surface, and a thirdportion that is opposite the second side surface; a plate portiondefining a plate trailing surface and a plate leading surface oppositethe plate trailing surface in a first direction, the plate portionconfigured to be coupled to the spacer portion such that the plateleading surface and the inner surface define an opening configured toreceive bone graft material.
 3. The intervertebral implant of claim 2,wherein the plate portion includes a first projection and a secondprojection that each extend from the plate leading surface in the firstdirection, each of first projection and the second projection configuredsuch that when the plate portion is coupled to the spacer portion aportion of the spacer portion is positioned between the first projectionand the second direction.
 4. The intervertebral implant of claim 3,wherein the spacer portion includes a first recess and a second recessthat are each configured to receive one of the first projection and thesecond projection to couple the spacer portion to the plate portion. 5.The intervertebral implant of claim 2, wherein the spacer portionincludes a first material, the plate portion includes a second material,and the first material is different than the second material.
 6. Theintervertebral implant of claim 5, wherein the first material is anon-metallic material and the second material is a metallic material. 7.The intervertebral implant of claim 2, wherein the spacer portiondefines a spacer top surface configured to face a first vertebral bodywhen the intervertebral implant is implanted and a spacer bottom surfaceconfigured to face a second vertebral body when the intervertebralimplant is implanted, the spacer bottom surface opposite the spacer topsurface in a second direction that is perpendicular to the firstdirection when the plate portion is coupled to the spacer portion, andthe opening extends through both the spacer top surface and the spacerbottom surface.
 8. The intervertebral implant of claim 2, wherein theplate portion includes a top surface configured to face a firstvertebral body when the intervertebral implant is implanted and a bottomsurface configured to face a second vertebral body when theintervertebral implant is implanted, the bottom surface opposite the topsurface along a second direction that is perpendicular to the firstdirection.
 9. The intervertebral implant of claim 8, wherein the plateportion defines a recess configured to receive an implant insertiontool, the recess partially defined by the plate trailing surface suchthat the recess extends into the plate trailing surface toward the plateleading surface and terminates at a first surface that faces in adirection opposite the first direction, and the recess partially definedby the top surface such that the recess extends into the top surface andterminates at a second surface that faces in a direction opposite thesecond direction.
 10. The intervertebral implant of claim 9, wherein therecess is a first recess, and the plate portion defines a second recessconfigured to receive the implant insertion tool, the second recesspartially defined by the plate trailing surface such that the secondrecess extends into the plate trailing surface toward the plate leadingsurface and terminates at a third surface that faces in the directionopposite the first direction, and the second recess partially defined bythe bottom surface such that the second recess extends into the bottomsurface and terminates at a fourth surface that faces in the seconddirection.
 11. An intervertebral implant comprising: a spacer portiondefining a spacer trailing surface and a spacer leading surface oppositethe spacer trailing surface; and a plate portion defining a platetrailing surface and a plate leading surface opposite the plate trailingsurface in a first direction, the plate portion further defining a topsurface, a bottom surface opposite the top surface in a seconddirection, and a plate body that extends from the plate trailing surfaceto the plate leading surface and that further extends from the topsurface to the bottom surface, the plate portion configured to becoupled to the spacer portion such that the plate leading surface facesthe spacer trailing surface, the plate portion defining a recessconfigured to receive an implant insertion tool, the recess partiallydefined by the plate trailing surface such that the recess extends intothe plate body toward the plate leading surface and terminates at afirst surface that faces in a direction opposite the first direction,and the recess partially defined by the top surface such that the recessextends into the plate body and terminates at a second surface thatfaces in a direction opposite the second direction.
 12. Theintervertebral implant of claim 11, wherein a first distance from thesecond surface to the top surface measured along a straight line that isparallel to the second direction is less than a second distance from thesecond surface to the bottom surface measured along the straight line.13. The intervertebral implant of claim 12, wherein a third distancefrom the first surface to the plate trailing surface measured along astraight line that is parallel to the first direction is less than afourth distance from the first surface to the plate leading surfacemeasured along the straight line that is parallel to the firstdirection.
 14. The intervertebral implant of claim 11, wherein therecess is a first recess, and the plate portion defines a second recessconfigured to receive the implant insertion tool, the second recesspartially defined by the plate trailing surface such that the secondrecess extends into the plate body toward the plate leading surface andterminates at a third surface that faces in the direction opposite thefirst direction, and the second recess partially defined by the bottomsurface such that the second recess extends into the plate body andterminates at a fourth surface that faces in the second direction. 15.The intervertebral implant of claim 14, wherein a first distance fromthe second surface to the top surface measured along a first straightline that is parallel to the second direction is less than a seconddistance from the second surface to the bottom surface measured alongthe first straight line, and a third distance from the fourth surface tothe bottom surface measured along a second straight line that isparallel to the second direction is less than a fourth distance from thefourth surface to the top surface measured along the second straightline.
 16. The intervertebral implant of claim 15, wherein the firstdistance is equal to the third distance, and the second distance isequal to the fourth distance.
 17. The intervertebral implant of claim15, wherein a fifth distance from the first surface to the platetrailing surface measured along a first straight line that is parallelto the first direction is less than a sixth distance from the firstsurface to the plate leading surface measured along the first straightline that is parallel to the first direction, and a seventh distancemeasured along a second straight line that is parallel to the firstdirection is less than an eighth distance from the first surface to theplate leading surface measured along the second straight line that isparallel to the first direction.
 18. The intervertebral implant of claim17, wherein the fifth distance is equal to the seventh distance, and thesixth distance is equal to the eighth distance.
 19. The intervertebralimplant of claim 14, wherein the intervertebral implant is configured tobe inserted in an intervertebral disc space between an upper vertebralbody and a lower vertebral body such that the top surface faces theupper vertebral body and the bottom surface faces the lower vertebralbody, and the plate portion defines a bone fixation hole configured toreceive a bone fixation element to secure the implant to one of thesuperior and inferior vertebral bodies.
 20. The intervertebral implantof claim 19, further comprising a retention mechanism configured toprevent a bone fixation element that is inserted in the bone fixationhole from backing out of the bone fixation hole.
 21. The intervertebralimplant of claim 20, wherein the retention mechanism includes a boreholethat is defined by the plate portion, and the borehole is spaced fromboth the first recess and the second recess.